When does morning sickness start, and when does it end?

When does morning sickness start?

ACOG says nausea and vomiting of pregnancy usually starts before 9 weeks of pregnancy (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025). Weeks of pregnancy are counted from the first day of the last period, so about two of them come before the pregnancy has begun (ACOG, "How Your Fetus Grows During Pregnancy", 2024). MedlinePlus counts from conception instead and says morning sickness often begins 4 to 6 weeks after conception (MedlinePlus, "Morning sickness", 2024), which is about 6 to 8 weeks on the usual count; that conversion is our arithmetic. Cleveland Clinic says it can start as early as the sixth week of pregnancy and that most women have signs of it before nine weeks (Cleveland Clinic, 2023).

A study that measured when morning sickness starts in pregnancy found an earlier average. Gadsby and colleagues asked 363 pregnant women to keep daily diaries of nausea and vomiting; all went on to have a single live baby. Symptoms began on average on day 39 after the last period, about 5 and a half weeks, and ended on average on day 84, 12 weeks (Gadsby et al., 1993). The conversions from days to weeks are our arithmetic.

How soon does morning sickness start, how early can morning sickness start, and what week does morning sickness start? The table sets out the answers, with when it is worst and when it ends, by source. When does pregnancy nausea start, when does nausea start in pregnancy and when does morning sickness start in pregnancy are the same question with the same answers.

The sources disagree mostly about the end, partly because they describe different things: a range for most women, an average, or the share of women who had relief by a given week. None of them is a deadline for one pregnancy. What week morning sickness starts for you is not something the table can say; it shows how wide the answers are. When do you get morning sickness, if you do? Anywhere inside them.

What morning sickness is

What is morning sickness? The NHS describes it as nausea and vomiting in pregnancy, very common in early pregnancy, which can affect you at any time of the day or night, or as feeling sick all day long (NHS, "Vomiting and morning sickness", 2024). The NHS page on severe vomiting says around 8 in 10 pregnant women feel sick, are sick, or both (NHS, "Severe vomiting in pregnancy", 2023), and in the UK the NHS also calls it pregnancy sickness (NHS, "Vomiting and morning sickness", 2024). ACOG says morning sickness in pregnancy can affect your life, including your ability to work or go about everyday activities (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025). Among morning sickness symptoms, MedlinePlus says some women also have dizziness and headaches (MedlinePlus, "Morning sickness", 2024).

Not just in the morning

Morning sickness at night, or all day, is common enough that the name misleads. In the Lacroix study, 160 women recorded nausea and vomiting every day: 74 in 100 had nausea, only 1.8 in 100 had it only in the morning, and 80 in 100 reported nausea lasting all day (Lacroix et al., 2000). In the Gadsby study, 80 in 100 women had symptoms, 28 in 100 nausea only and 52 in 100 nausea and vomiting, and 53 in 100 of the episodes of vomiting happened between 6 in the morning and noon (Gadsby et al., 1993). Pregnancy nausea, in other words, is often worse early in the day without being limited to it.

What it feels like

What does morning sickness feel like? ACOG says some women feel nauseated for a short time each day and may vomit once or twice, and that in more severe cases nausea lasts several hours each day and vomiting happens more often (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025). Lacroix and colleagues measured the nausea with a standard nausea questionnaire and found it similar in character and intensity to the nausea of patients having cancer chemotherapy (Lacroix et al., 2000). Cleveland Clinic says some women describe it as like heartburn or reflux, seasickness, something stuck in the throat, or hunger pangs (Cleveland Clinic, 2023). What does pregnancy nausea feel like for you? It varies, and these descriptions are not a test of whether you are pregnant.

When it peaks

When does morning sickness peak? In the Gadsby diaries, symptoms were at their peak in the ninth week (Gadsby et al., 1993). Cleveland Clinic says it is worst for most women at around 8 to 10 weeks, and that not everyone's symptoms peak at the same time (Cleveland Clinic, 2023). When morning sickness is the worst for any one person is not something either source predicts. The guide to 9 weeks pregnant covers what else the NHS describes that week.

When morning sickness ends

When does morning sickness end, and how long does morning sickness last? ACOG says it goes away by 14 weeks for most women, lasts several weeks or months for some, and lasts the whole pregnancy for a few (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025). The NHS says it usually clears up by weeks 16 to 20 (NHS, "Vomiting and morning sickness", 2024), and its page on severe vomiting says it improves or stops completely by around weeks 12 to 20 for most women, though for some it lasts longer (NHS, "Severe vomiting in pregnancy", 2023). MedlinePlus says it may continue until the fourth month of pregnancy (MedlinePlus, "Morning sickness", 2024).

The diary studies show the spread behind those ranges. In the Lacroix study, only 50 in 100 women had relief by 14 weeks, and 90 in 100 by 22 weeks (Lacroix et al., 2000). In the Gadsby study, symptoms ended on average on day 84, and for 40 in 100 women they stopped abruptly (Gadsby et al., 1993). When does nausea stop in pregnancy, and when does morning sickness go away? The answer varies by weeks, not days. The guides to 12 weeks pregnant and 13 weeks pregnant cover the weeks in which several of these sources place it easing.

What causes it

What causes morning sickness is not fully known. The NHS says hormonal changes in the first 12 weeks of pregnancy are probably one of the causes (NHS, "Vomiting and morning sickness", 2024). MedlinePlus says the exact cause is not known, that most experts think changing hormone levels cause it, and that an enhanced sense of smell and gastric reflux can make the nausea worse (MedlinePlus, "Morning sickness", 2024). What causes nausea in pregnancy, on these sources, is mainly hormonal, with no single hormone named.

The NHS lists factors that make morning sickness more likely: twins or more; severe sickness and vomiting in a previous pregnancy; a tendency to motion sickness; a history of migraine headaches; morning sickness in the family; having felt sick on contraceptives containing estrogen; a first pregnancy; and a BMI of 30 or more (NHS, "Vomiting and morning sickness", 2024). ACOG lists the risk factors for severe nausea and vomiting as a multiple pregnancy, nausea and vomiting in a previous pregnancy, a mother or sister who had severe nausea and vomiting in pregnancy, a history of motion sickness or migraines, and being pregnant with a female fetus (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025). These are patterns across many pregnancies and cannot tell anyone the sex of their own baby.

Hyperemesis gravidarum: when sickness is severe

Hyperemesis gravidarum, often shortened to HG, is the term for the most severe form of nausea and vomiting of pregnancy (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025). The NHS says it is not known exactly how many pregnant women have it, because some cases may go unreported, but that it is thought to be around 1 to 3 in 100 (NHS, "Severe vomiting in pregnancy", 2023). ACOG says it occurs in up to 3 in 100 pregnancies (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025).

The hyperemesis gravidarum symptoms the NHS lists are prolonged and severe nausea and vomiting, dehydration and weight loss. It describes dehydration as feeling thirsty, tired, dizzy or lightheaded, not peeing very much, and having dark yellow, strong-smelling pee. Unlike regular pregnancy sickness, it says, HG may not get better by 16 to 20 weeks and may not clear up completely until the baby is born, although some symptoms may improve at around 20 weeks, and it often needs hospital treatment (NHS, "Severe vomiting in pregnancy", 2023). ACOG says it may be diagnosed when a woman has lost 5 in 100 of her weight before pregnancy and has other problems related to dehydration, and that women with HG need treatment, sometimes in a hospital (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025).

Treatment is a decision for a doctor or midwife, and this guide does not cover medicines. The NHS advises seeing your GP or midwife if you have severe nausea and vomiting, because getting help early can help you avoid dehydration and weight loss (NHS, "Severe vomiting in pregnancy", 2023). Hyperemesis gravidarum sets out how UK and US health bodies define it, its warning signs and what happens at an assessment.

When to get help

The NHS advises calling your midwife or GP, or its urgent advice line, if you are vomiting and you (NHS, "Vomiting and morning sickness", 2024):

• have very dark urine or have not peed in more than 8 hours;
• cannot keep food or fluids down for 24 hours;
• feel very weak, dizzy or faint when standing up;
• have tummy pain;
• have a high temperature;
• vomit blood;
• have lost weight.

In the US, ACOG advises calling your ob-gyn or other obstetric care provider for signs of dehydration: a small amount of dark urine, being unable to urinate, being unable to keep liquids down, feeling dizzy or faint when standing up, or a racing or pounding heartbeat (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025). MedlinePlus adds vomiting blood or something that looks like coffee grounds, losing more than 2 pounds (1 kilogram) in a week, and severe vomiting that will not stop (MedlinePlus, "Morning sickness", 2024).

ACOG also says that nausea and vomiting that starts for the first time after 9 weeks, or comes with abdominal pain or tenderness, fever, headache or a swollen thyroid gland at the front of the neck, may point to another condition, such as an ulcer, a food-related illness, or thyroid or gallbladder disease (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025). The NHS says urinary tract infections can also cause nausea and vomiting (NHS, "Vomiting and morning sickness", 2024). For help with ordinary morning sickness, ACOG advises talking with your ob-gyn if it affects your life and causes you concern (ACOG, "Morning Sickness: Nausea and Vomiting of Pregnancy", 2025), and the NHS points to your GP or midwife.

Where morning sickness fits in the first weeks

Feeling or being sick is one of the early pregnancy symptoms the NHS lists, alongside tiredness, sore breasts and a missed period. The guide to 6 weeks pregnant covers what the NHS says about nausea that week. To see which week you are in, the pregnancy week calculator counts from the first day of your last period, and the due date calculator gives the date those weeks count toward.

This guide is information, not a diagnosis or a recommendation of treatment, and it is no substitute for your own clinician. See the medical disclaimer.